Despite our increased understanding of the determinants of substance abuse the treatment of addictive disorders continues to be a major public health problem. Even powerful treatments such as methadone maintenance for opiate dependence have high failure rates and, when patients stay in treatment, they often continue to use psychoactive substances. One reason for this poor outcome may be the high prevalence of comorbid psychiatric disorders in this population. Fortunately, a number of studies has shown the outcome of these patients can improve when their comorbidity is treated. Therefore, increasing the diagnostic accuracy and referral for treatment of this group of patients represents a promising strategy for the treatment of substance abuse disorders. As a first step in that process, this R03 proposal focuses on the adaptation and initial testing of the Patient Health Questionnaire (PHQ) for the diagnosis of psychiatric comorbidity in substance abuse patients, but it is not intended itself to change providers' behaviors. The PHQ is a brief, self-administered instrument that has been extensively studied in a variety of community-based, primary care medical settings. It has been found to accurately identify common psychiatric disorders and has been well accepted due its ease of use and low time demands on patients and staff. It is hoped that the adapted PHQ (Patient Health Questionnaire-Substance Abuse Version; PHQ-SA) will become a patient- and clinician-friendly tool for counselors and other frontline staff to identify patients who could benefit from referral for psychiatric care. Data from this study will help plan future intervention studies that will use our increased ability to diagnose comorbidity to provide appropriate referral and treatment strategies for substance abuse patients in community-based treatment settings.